Nowadays, the shallow diving systems used in oil exploitation and production offshore platforms that operate in deep waters are based and operated from the same unit where the inspecting work will be performed.
In offshore platforms the physical space is limited. After installing exploitation systems, their facilities, safety systems, accommodations, loading areas, winches, cranes, heliport and escape routes, there are few remaining spaces on board.
Diving systems in use are arranged in these remaining spaces, and they utilize as a transportation mean to access the submerse region, an open bottom diving bell or basket, that is kept suspended and vertically lowered by means of an articulated structure that extends outside the platform structure. These systems, however, can only control the open bottom diving bell positioning in the vertical direction, the necessary horizontal displacement is obtained by moving the divers away from it, at the depth work, by using an umbilical line that links them. Due to the few available space for installing the diving equipments, the distances between diving places and work places demand the use of long umbilical lines, that require a greater physical effort from the divers, and increase considerably the risk of the operation that may become unsafe or not be feasible in different points of the unit.
Many occurrences have demonstrated that the arrangements made for launching and rescuing the divers, as those used for shallow diving systems, located in platforms, could not guarantee the immediate rescue of injured/endangered divers.
Generally the only way for doing the rescue, is with the open bottom diving bell itself or the diving basket, that most of the time can not be placed where the diver is, or can not be immediately raised due to untangled umbilical lines and/or other reasons.
Floating production, storage and off-loading units, known as FPSO, that are authorized to operate for periods up to twenty years, without dry-docking, have their structural integrity verified by programmed sub aquatic surveys, together with non destructive test (NDT) inspection, in all the hull extension, and the execution of the repairs identified as necessary.
The activities comprised in the job for sub aquatic inspection and repairing demand a peculiar structure entirely dedicated, with facilities to give support to the divers' life and adequate working conditions, safety and effectiveness for the job.
The optimization of space on the production units clearly indicates that an improvement in the actual operating conditions for diving systems will be reached only with an evolution within the concept that overtakes the present critical points, listed bellow:                difficulty in rescuing the divers in an emergency situation;        short range for the horizontal reaching capability, limited by the umbilical line length that can be handled securely;        great difficulty to access different points of the platforms;        divers physical effort due to the use of long umbilical line;        necessity to move (re install) the support equipments;        there is the need of two men in the water: one man working, and the other to handle the umbilical line, from the open bottom diving bell or basket;        any emergency assistance or rescue activity become more difficult to provide since the other persons remain on the platform deck, 15 meters above;        delivering material and tools to the divers, at their work location;        job poor performance figures;        no space on the platforms for the installation of support equipments;        no accommodations for extra crew;        